In general, the use of shearing tools is very popular, especially, for gardening. While the functional development of shearing tools has been greatly upgraded, there are still some shortcomings in the popular shearing tools used nowadays, and thus, improvements are desirable. The listing below describes some of the disadvantages of popular shearing tools used today:
1. As shown in FIG. 1, this shearing tool is of a structure such that it can be operated by one hand. The structure includes two blades 2, each connected to a separate handle 1. The handles 1 are cross-connected by a hinged bolt. A compression spring 3 is installed between the two handles 1. The compression spring 3 makes the two handles 1 maintain a constant opening angle. When it is necessary to shear an item having a small diameter, the operator's hand needs to hold and compress both the handles 1 and the compression spring 3 first in order to reduce the opening angle of the blades 2 before the tool can begin to carry out the shearing action. This idle stroke of holding and compressing is useless with respect to the shearing action, and on the contrary; it causes waste of labor in applying the shearing force. Furthermore, the extent of opening of the blades is greatly limited, and therefore, this tool cannot be used for shearing items with a large diameter. This limitation greatly reduces the usefulness of this tool. PA0 2. As shown in FIG. 2, generally, this shearing tool is of a structure such that it is operated by two hands of the user. The upper blade portion 4 is connected to the handle 5, while the lower blade portion 6 is hinge-connected to the handle 8 through a connecting rod 7. Moreover, one end of the handle 8 is hinge-connected to the upper blade portion 4. The benefits of this tool, however, cannot be fully used when it comes to cutting items with a small diameter owing to the reason that its benefit in applying shearing force is at a maximum when the handle 8 extends at an appropriate opening angle. On the contrary, it is inconvenient to apply force with this tool when it is necessary to cut items with a small diameter and the handles 5 and 8 are opened only at a small opening angle. Similarly, this same problem will occur before one finishes cutting items with a large diameter. Moreover, in cutting items with a large diameter, the handle 8 must be opened at a large opening angle, which will result in wasted labor and is inconvenient for the operator during the shearing operation. Therefore, this tool also needs to be improved.
In view of this situation, the inventor, with his accumulated years of working experience and through his persistent study in design works, developed a shearing tool that can automatically adjust depending on the sectional dimension of the items to be cut by controlling the extent that the handles need to open and by keeping the handles in the range of the optimum shearing angle opening for attaining the maximum shearing benefit. This is the aim of the design of the present invention.